1. Field of the Invention
The invention relates to a composite material tube and, in particular, to an angle-laminated composite tube with double layer of materials.
2. Related Art
Phenolic resin composite materials are conventionally known for its thermal insulating and flame retardant characteristics, and are conventionally used in aerospace and defense industries, such as fireproof materials in commercial aircrafts, thermal insulator in missiles and rocket launching systems, heat shields of metallic structures in human or unmanned space vehicles, etc.
Carbon fiber fabrics and phenolic resin are usually combined to form a composite material that has advantageous mechanical and thermal properties, the carbon fiber fabrics being able to resist to temperatures above 2000° C. within a short duration and offer superior mechanical strength. This type of composite materials thus has become the principal thermal insulator in aerospace and defense technologies. Industrialized countries thus have put major investments in the development of this material with respect to every aspect including the raw material, the manufacture process, or the assembly of component parts.
U.S. Pat. No. 6,013,361 disclosed an autoclave process for manufacturing a carbon fabric reinforced phenolic resin composite which has porosity of at least 4% by volume. Network pores of the composite material allow of volatile gas escape. When the composite material is heated, the volatile formed by decomposition of phenolic resin in the composite material at high temperature is released via the network pores, so that the composite material can sustain a sufficient strength under high temperature. This type of composite material can be used in fireproof structures of Space Shuttles.
In the reference of Recent Advances in Composites Materials(ASME MD-Vol 56, 1995) disclosed by Daewoo Heavy Industries, Ltd, the ablative heat shield of a rocket launching system applies a composite thermal insulating structure, composed of a sandwich structure design, which is surface coated with a 15 mm-thick parallel laminated carbon fiber fabric reinforced phenolic resin composite by autoclave process.
In addition to the influence of the raw material and the manufacture process on characteristics of the carbon fabric reinforced phenolic resin composite, the external heat source and the orientation of fiber are also factors which determine the thermal insulating characteristics of the composite. The AIAA-89-2418 reference indicates that the 3.7 m diameter solid rocket booster (SRB) of Space Shuttle uses an ablative throat insert made of carbon fabric reinforced phenolic resin composite material, which the optimal angles between the plies and the flame surface in SRB nozzles has been proven to be between 30 degrees and 60 degrees, depending upon the location, contour and heating conditions at various sections of the nozzle.
NASA PD-ED-1218 discloses a rocket nozzle in which an ablative part with ply angle of 45 degree is manufactured by using a tape wrapper to attach 45 degree bias-cut tapes over a mandrel and curing with a hydroclave.
U.S. patent application Ser. No. 11/002,152 discloses a method to fabricate a laminated composite tube with an arranged ply angle. In this method, carbon fabric reinforced phenolic prepregs were first cut into fan-shaped pieces and laminated in a mold including a concave female mold and a convex male mold both have a tapered angle Φ. Hot press molding with pressure over 140.6 kg/cm2 is then used for solidifying the lamina assembly to get the composite hollow cylinder with arranged ply angle Φ.
The techniques disclosed in the above-mentioned patent and references are used in making the thermal insulating layer components of nozzles. Using the carbon fiber fabric reinforced phenolic resin prepregs along with an appropriately designed ply angle can achieve the required ablation resistance. However, it is still insufficient for thermal insulation. Therefore, they have to be covered with a thermal insulating layer to protect the metal structure outside it, thus forms a double-layer structure. The reference AIAA-89-2418 shows that the U.S. space shuttle uses glass or silica fiber reinforced phenolic resin composite as the thermal insulation of the carbon fiber reinforced phenolic resin composite liner. The production method is to apply a coat of phenolic resin on the machined surface of the cured carbon phenolic composite, followed by tape wrapping the glass of silica phenolic tape, and finally the second curing process by autoclave. Instead of the second curing process, the angle-laminated composite tube disclosed in U.S. patent application Ser. No. 11/002,152 uses carbon phenolic and silica phenolic composite materials produced separately. Each of them is machined before being combined using an adhesive to form a double-layer structure. These prior arts require either second curing or additional machining and gluing processes, costing a lot of manpower. Moreover, if the inner and outer layers differ very much in properties, then there may remain an extremely high thermal stress at the interface. More seriously, the interface may crack and affect its strength. These are problems to be solved.